Phosphoenolpyruvate Phosphotransferase System Components Modulate Gene Transcription and Virulence of Borrelia burgdorferi

Abstract

The phosphoenolpyruvate phosphotransferase system (PEP-PTS) and adenylate cyclase (AC) IV (encoded by BB0723 [cyaB]) are well conserved in different species of Borrelia. However, the functional roles of PEP-PTS and AC in the infectious cycle of Borrelia have not been characterized previously. We examined 12 PEP-PTS transporter component mutants by needle inoculation of mice to assess their ability to cause mouse infection. Transposon mutants with mutations in the EIIBC components (ptsG) (BB0645, thought to be involved in glucose-specific transport) were unable to cause infection in mice, while all other tested PEP-PTS mutants retained infectivity. Infectivity was partially restored in an in trans-complemented strain of the ptsG mutant. While the ptsG mutant survived normally in unfed as well as fed ticks, it was unable to cause infection in mice by tick transmission, suggesting that the function of ptsG is essential to establish infection by either needle inoculation or tick transmission. In Gramnegative organisms, the regulatory effects of the PEP-PTS are mediated by adenylate cyclase and cyclic AMP (cAMP) levels. A recombinant protein encoded by B. burgdorferi BB0723 (a putative cyaB homolog) was shown to have adenylate cyclase activity in vitro; however, mutants with mutations in this gene were fully infectious in the tick-mouse infection cycle, indicating that its function is not required in this process. By transcriptome analysis, we demonstrated that the ptsG gene may directly or indirectly modulate gene expression of Borrelia burgdorferi. Overall, the PEP-PTS glucose transporter PtsG appears to play important roles in the pathogenesis of B. burgdorferi that extend beyond its transport functions.

A high-throughput genetic screen identifies previously uncharacterized Borrelia burgdorferi genes important for resistance against reactive oxygen and nitrogen species

“…Several of the mutants included in our mini-library have also been tested in single strain infections (for example, uvrC , uvrD , pdeA , and cyaB ) [34, 41, 66]. Again, our results are largely consistent with the results of these previous studies, and differences in the nature of single-strain versus competition experiments could explain some minor discrepancies [66]. …”

“…For example, earlier signature tagged mutagenesis or Tn-seq screens included Tn mutants with insertions in 19 of the same genes as the Tn mutants included in our mini-library; 17 of these 19 mutants had at least partial infectivity defects in both studies [30, 32]. Several of the mutants included in our mini-library have also been tested in single strain infections (for example, uvrC , uvrD , pdeA , and cyaB ) [34, 41, 66]. Again, our results are largely consistent with the results of these previous studies, and differences in the nature of single-strain versus competition experiments could explain some minor discrepancies [66].…”

“…It is important to note that there is not perfect concordance between the Tn mutants represented in our Tn-seq dataset and the Tn mutants available in the arrayed library. This is primarily a result of four factors: (1) the exclusion of Tn mutants from the Tn-seq data analysis due to low representation in the library; (2) the loss of Tn mutants from the population when the library was originally pooled; (3) the presence of co-isolates in some of the previously described Tn mutants [32, 66]; and (4) the inclusion of Tn mutants in the pooled library for which the insertion site had not been mapped. All individual Tn mutants were screened by polymerase chain reaction (PCR) at the locus of interest to confirm pure populations.…”

Interaction of the Lyme disease spirochete with its tick vector

“…Glucose-6-phosphate is then funneled into glycolysis for energy generation or used as a substrate for synthesis of membrane phospholipids, lipoproteins and nucleic acids (Gherardini et al, 2010). Recently, Khajanchi et al (2016) demonstrated that ptsG mutants are avirulent in mice by syringe inoculation, suggesting that spirochetes rely heavily on this transporter in vivo . In ticks, spirochetes must compete for blood meal-derived glucose with rapidly differentiating midgut epithelial cells that are avidly engulfing the blood meal.…”

Gene bb0318 Is Critical for the Oxidative Stress Response and Infectivity of Borrelia burgdorferi

“…The utilization of transport systems to obtain biomolecules as precursors for essential metabolic processes is likely critical to the survival of B. burgdorferi throughout its infectious life cycle. Indeed, a subset of B. burgdorferi nutrient uptake systems has been demonstrated to play important roles in spirochete survival in vivo (5)(6)(7)(8). This finding, as well as the fact that this spirochete lacks classical virulence factors, suggests that the ability of B. burgdorferi to scavenge nutrients and metabolites is not only a survival mechanism but also a significant component of B. burgdorferi pathogenesis.…”